Metal-air battery having folded structure and method of manufacturing the same

ABSTRACT

A metal-air battery including: a negative electrode metal layer; a negative electrode electrolyte layer disposed on the negative electrode metal layer; a positive electrode layer disposed on the negative electrode electrolyte layer, the positive electrode layer comprising a positive electrode material which is capable of using oxygen as an active material; and a gas diffusion layer disposed on the positive electrode layer, wherein the negative electrode electrolyte layer is between the negative electrode metal layer and the positive electrode layer; wherein the negative electrode metal layer, the negative electrode electrolyte layer, and the positive electrode layer are disposed on the gas diffusion layer so that the positive electrode layer contacts a lower surface and an opposite upper surface of the gas diffusion layer, and wherein one side surface of the gas diffusion layer is exposed to an outside.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.15/335,645, filed on Oct. 27, 2016, which is a continuation of U.S.patent application Ser. No. 14/310,572, filed on Jun. 20, 2014, whichclaims priority to and the benefit of Korean Patent Application No.10-2013-0140083, filed on Nov. 18, 2013, in the Korean IntellectualProperty Office, and all the benefits accruing therefrom under 35 U.S.C.§ 119, the content of which is incorporated herein in its entirety byreference.

BACKGROUND 1. Field

The present disclosure relates to a metal-air battery and a method ofmanufacturing the same, and more particularly, to a metal-air batteryhaving increased energy density, and a method of manufacturing the same.

2. Description of the Related Art

A metal-air battery includes a negative electrode capable of occludingand emitting ions and a positive electrode in which oxygen in the air isused as an active material. In the metal-air battery, reduction andoxidation reactions of oxygen received from the outside occur in thepositive electrode, oxidation and reduction reactions of the metal occurin the negative electrode, and chemical energy generated then isextracted as electrical energy. For example, the metal-air batteryabsorbs oxygen during discharge and emits oxygen during charge. Asdescribed above, since the metal-air battery uses oxygen in the air,energy density of the metal-air battery may be significantly greaterthan that of other batteries. For example, the metal-air battery mayhave an energy density several times higher than that of a conventionallithium ion battery.

In addition, since the metal-air battery has a low probability ofignition caused by an abnormally high temperature, the metal-air batteryhas high stability and, since the metal-air battery is operated by onlyabsorption and emission of oxygen without using a heavy metal, there isa low probability of the metal-air battery contaminating theenvironment. Due to such various advantages, much research into themetal-air battery is currently being performed, and the remains a needfor improved metal-air battery.

SUMMARY

According to an exemplary embodiment, a metal-air battery includes anegative electrode metal layer, a negative electrode electrolyte layerdisposed on the negative electrode metal layer, a positive electrodelayer disposed on the negative electrode electrolyte layer, the positiveelectrode layer comprising a positive electrode material which iscapable of using oxygen as an active material, and a gas diffusion layerdisposed on the positive electrode layer, wherein the negative electrodeelectrolyte layer is between the negative electrode metal layer and thepositive electrode layer, wherein the negative electrode metal layer,the negative electrode electrolyte layer, and the positive electrodelayer are disposed on the gas diffusion layer so that the positiveelectrode layer contacts a lower surface and an opposite upper surfaceof the gas diffusion layer, and wherein one side surface of the gasdiffusion layer is exposed to an outside.

The gas diffusion layer may include a plurality of gas diffusion layers.The negative electrode metal layer, the negative electrode electrolytelayer, and the positive electrode layer may be repeatedly bent so thatthe positive electrode layer contacts lower and upper surfaces of theplurality of gas diffusion layers.

Between two adjacent gas diffusion layers, the negative electrode metallayer, the negative electrode electrolyte layer, and the positiveelectrode layer may be bent by 180 degrees so that the negativeelectrode metal layer is in a folded configuration and the positiveelectrode layer contacts the two adjacent gas diffusion layers.

The same side surfaces of the plurality of gas diffusion layers may bealways exposed to the outside.

The metal-air battery may further include a negative electrode collectorarranged to contact a bend portion of the bent negative electrode metallayer.

The negative electrode collector may extend in a direction perpendicularto a layer direction of the negative electrode metal layer, the negativeelectrode electrolyte layer, the positive electrode layer, and the gasdiffusion layer.

A ratio of a weight of the negative electrode collector to the totalweight of the metal-air battery may be smaller than, for example, about10%.

The metal-air battery may further include an outer casing that surroundssurfaces of the negative electrode metal layer, the negative electrodeelectrolyte layer, the positive electrode layer, and the gas diffusionlayers except for the exposed side surfaces of the gas diffusion layer.

The negative electrode collector may be positioned between the negativeelectrode metal layer and the outer casing in the outer casing.

An end of the exposed side surface of the gas diffusion layer mayprotrude from the negative electrode metal layer, the negative electrodeelectrolyte layer, and the positive electrode layer.

The metal-air battery may further include a positive electrode collectorconnected to the protruding end of the gas diffusion layer.

The negative electrode electrolyte layer may include a separation layerwhich is ionically conductive and is substantially impermeable tooxygen, and an electrolyte for transmitting the metal ions.

The separation layer may include a porous layer and pores of the porouslayer may be impregnated with the electrolyte.

According to another exemplary embodiment, a metal-air battery includes:a negative electrode metal layer, a negative electrode electrolyte layerdisposed on the negative electrode metal layer, a first positiveelectrode layer disposed on a first portion of the negative electrodeelectrolyte layer, the positive electrode layer comprising a positiveelectrode material which is capable of using oxygen as an activematerial, a gas diffusion layer disposed on the first positive electrodelayer, and a second positive electrode layer disposed on the gasdiffusion layer and opposite the first positive electrode layer, whereina first portion of the negative electrode electrolyte layer is betweenthe first positive electrode layer and a first portion of the negativeelectrode metal layer, and a second portion of the negative electrodeelectrolyte layer is between the second positive electrode layer and asecond portion of the negative electrode electrolyte layer, wherein thenegative electrode metal layer and the negative electrode electrolytelayer are disposed on the first and second positive electrode layers sothat the negative electrode electrolyte layer contacts a lower surfaceof the first positive electrode layer and an upper surface of the secondpositive electrode layer, and wherein one side surface of the gasdiffusion layer is exposed to the outside.

Lower and upper surfaces of the gas diffusion layer may be coated withthe first and second positive electrode layers, respectively.

The gas diffusion layer may include a plurality of gas diffusion layerswhose lower and upper surfaces are coated with the first and secondpositive electrode layers, respectively. The negative electrode metallayer and the negative electrode electrolyte layer may be repeatedlybent so that the negative electrode electrolyte layer contacts the firstpositive electrode layer and the second positive electrode layer.

Between two adjacent gas diffusion layers, the negative electrode metallayer and the negative electrode electrolyte layer may be bent by 180degrees so that the negative electrode metal layer is in a foldedconfiguration and the negative electrode electrolyte layer contacts thefirst positive electrode layer and the second positive electrode layer.

According to another exemplary embodiment, a method of manufacturing ametal-air battery includes: disposing a negative electrode electrolytelayer on a negative electrode metal layer, disposing a positiveelectrode layer which is capable of using oxygen as an active materialon the negative electrode electrolyte layer, disposing a gas diffusionlayer on the positive electrode layer, and bending the negativeelectrode metal layer, the negative electrode electrolyte layer, and thepositive electrode layer on the gas diffusion layer so that the positiveelectrode layer contacts a lower surface and an opposite upper surfaceof the gas diffusion layer, wherein one side surface of the gasdiffusion layer is exposed to the outside.

The method may further include bending the negative electrode metallayer, the negative electrode electrolyte layer, and the positiveelectrode layer by 180 degrees so that the negative electrode metallayer is folded and the positive electrode layer is exposed upward,partially arranging an additional gas diffusion layer on the positiveelectrode layer, and bending the negative electrode metal layer, thenegative electrode electrolyte layer, and the positive electrode layeron the additional gas diffusion layer so that the positive electrodelayer contacts an upper surface of the additional gas diffusion layer.

According to another exemplary embodiment, a method of manufacturing ametal-air battery may include arranging a negative electrode electrolytelayer on a negative electrode metal layer, providing a gas diffusionlayer whose lower and upper surfaces are coated with a first positiveelectrode layer and a second positive electrode layer, respectively;partially arranging the gas diffusion layer on the negative electrodeelectrolyte layer so that the first positive electrode layer on thelower surface of the gas diffusion layer contacts the negative electrodeelectrolyte layer, and bending the negative electrode metal layer andthe negative electrode electrolyte layer on the gas diffusion layer sothat the negative electrode electrolyte layer contacts the secondpositive electrode layer on the upper surface of the gas diffusionlayer, wherein one side surface of the gas diffusion layer may beexposed to the outside.

The method of manufacturing a metal-air battery may further includebending the negative electrode metal layer and the negative electrodeelectrolyte layer by 180 degrees so that the negative electrode metallayer is folded and the negative electrode electrolyte layer is exposedupward, partially arranging an additional gas diffusion layer whoselower and upper surfaces are coated with the first positive electrodelayer and the second positive electrode layer, respectively, on thenegative electrode electrolyte layer, and bending the negative electrodemetal layer and the negative electrode electrolyte layer on theadditional gas diffusion layer so that the negative electrodeelectrolyte layer contacts the second positive electrode layer on theupper surface of the additional gas diffusion layer.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects will become apparent and more readilyappreciated from the following description of the embodiments, taken inconjunction with the accompanying drawings in which:

FIG. 1 is a perspective view schematically illustrating a structure ofan embodiment of a metal-air battery having a folded structure;

FIG. 2 is a perspective view schematically illustrating a structure of asingle cell metal-air battery;

FIG. 3A is a perspective view schematically illustrating a structure ofan embodiment of a metal-air battery having a folded structure in whichthe number of cells is increased;

FIG. 3B is a perspective view schematically illustrating a structure ofan end cell of the metal-air battery of FIG. 3A;

FIG. 3C is a perspective view schematically illustrating a structure ofa unit middle cell of the metal-air battery of FIG. 3A;

FIG. 4 is a perspective view schematically illustrating a structure ofanother embodiment of a metal-air battery having a folded structure inwhich the number of cells is increased;

FIG. 5 is a cross-sectional view schematically illustrating a state inwhich an embodiment of a negative electrode collector and an outercasing are further disposed on the metal-air battery of FIG. 1;

FIG. 6 is a cross-sectional view schematically illustrating a structureof another embodiment of a metal-air battery;

FIG. 7 is a cross-sectional view schematically illustrating a structureof another embodiment of a metal-air battery;

FIGS. 8A to 8E are cross-sectional views schematically illustrating anembodiment of a process of manufacturing the metal-air battery of FIG.1;

FIGS. 9A to 9C are cross-sectional views schematically illustrating anembodiment of a process of manufacturing the metal-air battery of FIG.7;

FIG. 10 is a cross-sectional view schematically illustrating a structureof a metal-air battery in the form of a two-dimensional cell accordingto a Comparative Example; and

FIG. 11 is a graph of energy density (watt-hours per kilogram (Wh/kg))of the metal-air battery of the Example and Comparative Example; and

FIG. 12 is a graph of energy density (Wh/kg) versus cycle numberillustrating the energy density of the metal-air battery of FIG. 1.

DETAILED DESCRIPTION

A metal-air battery having a folded structure and a method ofmanufacturing the same now will be described more fully hereinafter withreference to the accompanying drawings, in which elements of theinventive concept are shown. The inventive concept may, however, beembodied in many different forms and should not be construed as limitedto the exemplary embodiments set forth herein. Rather, these embodimentsare provided so that this disclosure will be thorough and complete, andwill fully convey the scope of the disclosure to one of ordinary skillin the art. In the drawings, the thickness of layers and regions areexaggerated for clarity.

It will also be understood that when a layer is referred to as being“on” another layer or substrate, it can be directly on the other layeror substrate, or intervening layers may also be present therebetween. Incontrast, when an element is referred to as being “directly on” anotherelement, there are no intervening elements present. The same referencenumerals in different drawings represent the same element.

It will be understood that, although the terms “first,” “second,”“third,” etc. may be used herein to describe various elements,components, regions, layers, and/or sections, these elements,components, regions, layers, and/or sections should not be limited bythese terms. These terms are only used to distinguish one element,component, region, layer, or section from another element, component,region, layer, or section. Thus, “a first element,” “component,”“region,” “layer,” or “section” discussed below could be termed a secondelement, component, region, layer, or section without departing from theteachings herein.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting. As used herein, thesingular forms “a,” “an,” and “the” are intended to include the pluralforms, including “at least one,” unless the content clearly indicatesotherwise. “Or” means “and/or.” As used herein, the term “and/or”includes any and all combinations of one or more of the associatedlisted items. It will be further understood that the terms “comprises”and/or “comprising,” or “includes” and/or “including” when used in thisspecification, specify the presence of stated features, regions,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,regions, integers, steps, operations, elements, components, and/orgroups thereof.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper,” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

“About” or “approximately” as used herein is inclusive of the statedvalue and means within an acceptable range of deviation for theparticular value as determined by one of ordinary skill in the art,considering the measurement in question and the error associated withmeasurement of the particular quantity (i.e., the limitations of themeasurement system). For example, “about” can mean within one or morestandard deviations, or within ±30%, 20%, 10%, 5% of the stated value.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. It willbe further understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and thepresent disclosure, and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

Exemplary embodiments are described herein with reference to crosssection illustrations that are schematic illustrations of idealizedembodiments. As such, variations from the shapes of the illustrations asa result, for example, of manufacturing techniques and/or tolerances,are to be expected. Thus, embodiments described herein should not beconstrued as limited to the particular shapes of regions as illustratedherein but are to include deviations in shapes that result, for example,from manufacturing. For example, a region illustrated or described asflat may, typically, have rough and/or nonlinear features. Moreover,sharp angles that are illustrated may be rounded. Thus, the regionsillustrated in the figures are schematic in nature and their shapes arenot intended to illustrate the precise shape of a region and are notintended to limit the scope of the present claims.

FIG. 1 is a perspective view schematically illustrating a structure ofan embodiment of a metal-air battery 10 having a folded structure.Referring to FIG. 1, the metal-air battery 10 may include a negativeelectrode metal layer 11, a negative electrode electrolyte layer 12, apositive electrode layer 13, and at least one gas diffusion layer, forexample, first and second gas diffusion layers 14 a and 14 b. Here, thenegative electrode metal layer 11, the negative electrode electrolytelayer 12, and the positive electrode layer 13 are bent to surround threesurfaces of the first and second gas diffusion layers 14 a and 14 b, forexample the lower 14 c, inner 14 d, and upper 14 e surfaces of each ofthe first and second gas diffusion layers. For example, after partiallydisposing, e.g., arranging, the first gas diffusion layer 14 a on thepositive electrode layer 13, the negative electrode metal layer 11, thenegative electrode electrolyte layer 12, and the positive electrodelayer 13 may be bent on the first gas diffusion layer 14 a so that thepositive electrode layer 13 contacts an upper surface and a lowersurface of the first gas diffusion layer 14 a.

Then, after the negative electrode metal layer 11, the negativeelectrode electrolyte layer 12, and the positive electrode layer 13 arereversely folded by 180 degrees so that the positive electrode layer 13faces upward, the second gas diffusion layer 14 b may be furtherdisposed on the positive electrode layer 13. The negative electrodemetal layer 11, the negative electrode electrolyte layer 12, and thepositive electrode layer 13 may then be bent on the second gas diffusionlayer 14 b so that the positive electrode layer 13 contacts an uppersurface and a lower surface of the second gas diffusion layer 14 b. Inthe metal-air battery 10 illustrated in FIG. 1, only the negativeelectrode metal layer 11 is shown on the right-hand side of themetal-air battery 10, and the negative electrode electrolyte layer 12,the positive electrode layer 13, and the first and second gas diffusionlayers 14 a and 14 b may be exposed on the left-hand side of themetal-air battery 10. Therefore, oxygen, which is used for the oxidationand reduction reactions in the positive electrode layer 13, may beabsorbed from the left-hand side of the first and second gas diffusionlayers 14 a and 14 b in the orientation of FIG. 1 so that oxygen issupplied to an entire region of the positive electrode layer 13.

In FIG. 1, in order to facilitate understanding of the folded structureof the metal-air battery 10 according to the present embodiment, the twogas diffusion layers, namely, the first and second gas diffusion layers14 a and 14 b, are illustrated. However, any number of repeat units maybe used. The metal-air battery 10 illustrated in FIG. 1 includes twofolded-type cells.

Shown in FIG. 2 is a metal-air battery comprising a single unit. In themetal air battery of FIG. 2, three surfaces of the first gas diffusionlayer 14 a are surrounded by the negative electrode metal layer 11, thenegative electrode electrolyte layer 12, and the positive electrodelayer 13, as illustrated in FIG. 2. Therefore, it may be considered thatthe metal-air battery 10 illustrated in FIG. 1 includes two folded-typecells.

As described above, a process of arranging the first and second gasdiffusion layers 14 a and 14 b on the positive electrode layer 13 andbending the negative electrode metal layer 11, the negative electrodeelectrolyte layer 12, and the positive electrode layer 13 may berepeated to increase the number of cells of the metal-air battery 10.For example, FIG. 3A is a perspective view schematically illustrating astructure in which the number of cells is increased. Although theprocess of disposing the first and second gas diffusion layers 14 a and14 b on the positive electrode layer 13 and bending the negativeelectrode metal layer 11, the negative electrode electrolyte layer 12,and the positive electrode layer 13 is repeated so that the number ofcells is increased, as illustrated in FIG. 3A, portions of the first andsecond gas diffusion layers 14 a and 14 b are always exposed to theoutside. For example, in FIG. 3A, the portion of the surfaces of thefirst and second gas diffusion layers 14 a and 14 b shown at the frontof the battery, e.g., the side including the bend 10A, are covered withan outer casing 16 when the metal-air battery 10 is wrapped by the outercasing 16 (refer to FIG. 5), however, the surface on the left side ofthe first and second gas diffusion layers 14 a and 14 b may be alwaysexposed to the outside although the metal-air battery 10 is partiallywrapped by the outer casing 16. Therefore, according to the presentembodiment, in the metal-air battery 10, oxygen may be easily suppliedto the positive electrode layer 13 regardless of the increase in thenumber of cells.

In FIG. 3A, an example, in which the process of windingly bending thenegative electrode metal layer 11, the negative electrode electrolytelayer 12, and the positive electrode layer 13 is repeated a plurality oftimes to increase the number of cells, is illustrated. The metal airbattery may comprise an end cell as shown in FIG. 3B on either end ofthe structure, and a plurality of middle cells as shown in FIG. 3Cbetween the end cells. The number of cells may be increased by anothermethod. For example, as illustrated in FIG. 4, the metal-air battery 10having two cells, which is illustrated in FIG. 1, may be stacked aplurality of times to increase the number of cells. In addition, themetal-air battery 10 having one cell, which is illustrated in FIG. 2,may be stacked a plurality of times to increase the number of cells.

FIG. 5 is a cross-sectional view schematically illustrating aconfiguration which a negative electrode collector 15 and an outercasing 16 are further disposed on the metal-air battery 10 of FIG. 1.Referring to FIG. 5, the negative electrode collector 15 is arranged ona right-hand region of the metal-air battery 10, where the negativeelectrode metal layer 11 is bent, such that the negative electrodecollector 15 contacts a bend 51 of the negative electrode metal layer11. The negative electrode collector 15 may comprise a conductive metalsuch as copper (Cu), and may be in the form of a thin film or layer ofthe conductive metal. As illustrated in FIG. 5, the negative electrodecollector 15 may extend in a direction perpendicular to a layerdirection, i.e., a major surface, of the negative electrode metal layer11, the negative electrode electrolyte layer 12, the positive electrodelayer 13, and/or the first and second gas diffusion layers 14 a and 14b. Since the negative electrode collector 15 flatly extends in avertical direction without being bent regardless of the number of cells,an amount of material of the negative electrode collector 15 may bereduced and a ratio of a weight of the negative electrode collector 15to a weight of the metal-air battery 10 may be reduced. For example, aratio of a weight of the negative electrode collector 15 to the totalweight of the metal-air battery 10 excluding the outer casing 16 may beno more than about 10% or about 5%, for example about 1% to about 10%,or about 2% to about 5%, based on a total weight of the metal-airbattery.

A lower surface, a right-hand surface, and an upper surface of themetal-air battery 10 may be surrounded by the outer casing 16, which maybe in the form of a pouch, and may comprise a film material. Althoughnot shown in FIG. 5, front and rear surfaces of the metal-air battery 10may be also surrounded by the outer casing 16. That is, five surfaces ofthe metal-air battery 10 may be surrounded by the outer casing 16, and asixth, e.g. left-hand side surface 52, maybe exposed. That is, surfacesof the negative electrode metal layer 11, the negative electrodeelectrolyte layer 12, the positive electrode layer 13, and the first andsecond gas diffusion layers 14 a and 14 b, excluding the exposed sidesurfaces of the first and second gas diffusion layers 14 a and 14 b, maybe surrounded by the outer casing 16. When the metal-air battery 10 issurrounded by the outer casing 16, the negative electrode collector 15is positioned between the negative electrode metal layer 11 and theouter casing 16 and in the outer casing 16. Since the left side surfaceof the metal-air battery 10 is not surrounded by the outer casing 16,the first and second gas diffusion layers 14 a and 14 b may be exposedto the outside on the left of the metal-air battery 10.

FIG. 6 is a cross-sectional view schematically illustrating a structureof another embodiment of a metal-air battery 10. In the above-describedembodiment, exposed left ends of the first and second gas diffusionlayers 14 a and 14 b are formed to coincide with left surfaces of thenegative electrode metal layer 11, the negative electrode electrolytelayer 12, and the positive electrode layer 13. However, as illustratedin FIG. 6, the first and second gas diffusion layers 14 a and 14 b maybe formed so that the exposed left ends thereof protrude from the leftsurfaces of the negative electrode metal layer 11, the negativeelectrode electrolyte layer 12, and the positive electrode layer 13.Therefore, a larger area of the first and second gas diffusion layers 14a and 14 b contacts external air so that oxygen may be more smoothlysupplied to the positive electrode layer 13. In addition, as illustratedin FIG. 6, a positive electrode collector 17 is connected to theprotruding ends of the first and second gas diffusion layers 14 a and 14b so that current may be easily output from the positive electrode layer13.

FIG. 7 is a cross-sectional view schematically illustrating a structureof a metal-air battery 20 according to another embodiment. In theabove-described embodiment, the first and second gas diffusion layers 14a and 14 b are separately formed from the positive electrode layer 13 sothat the negative electrode metal layer 11, the negative electrodeelectrolyte layer 12, and the positive electrode layer 13 are bent tosurround the three surfaces of the first and second gas diffusion layers14 a and 14 b. However, in the embodiment illustrated in FIG. 7, thefirst and second gas diffusion layers 14 a and 14 b and first and secondpositive electrode layers 13 a and 13 b may be integrally formed. Forexample, lower surfaces of the first and second gas diffusion layers 14a and 14 b may be coated with the first positive electrode layer 13 a,and upper surfaces of the first and second gas diffusion layers 14 a and14 b may be coated with the second positive electrode layer 13 b. Inthis case, as illustrated in FIG. 7, the negative electrode metal layer11 and the negative electrode electrolyte layer 12 are bent to surrounda lower surface of the first positive electrode layer 13 a and an uppersurface of the second positive electrode layer 13 b. For example, afterthe first gas diffusion layer 14 a coated with the first positiveelectrode layer 13 a and the second positive electrode layer 13 b ispartially disposed on the negative electrode electrolyte layer 12, thenegative electrode metal layer 11 and the negative electrode electrolytelayer 12 may be disposed, e.g., bent on the second positive electrodelayer 13 b so that the negative electrode electrolyte layer 12 contactsthe upper surface of the second positive electrode layer 13 b.

Then, after the negative electrode metal layer 11 and the negativeelectrode electrolyte layer 12 are reversely folded by 180 degrees sothat the negative electrode electrolyte layer 12 faces upward, thesecond gas diffusion layer 14 b may be further disposed on the negativeelectrode electrolyte layer 12. The lower and upper surfaces of thesecond gas diffusion layer 14 b are contacted, e.g., coated, with thefirst and second positive electrode layers 13 a and 13 b, respectively,so that the first positive electrode layer 13 a contacts the negativeelectrode electrolyte layer 12. The negative electrode metal layer 11and the negative electrode electrolyte layer 12 may be disposed, e.g.,bent, on the second positive electrode layer 13 b so that the negativeelectrode electrolyte layer 12 contacts the second positive electrodelayer 13 b on the upper surface of the second gas diffusion layer 14 b.

FIGS. 8A to 8E are cross-sectional views schematically illustratingprocesses of manufacturing the metal-air battery 10 of FIG. 1. FIGS. 9Ato 9C are cross-sectional views schematically illustrating processes ofmanufacturing the metal-air battery 20 of FIG. 7. Hereinafter, methodsof manufacturing the above-described metal-air batteries 10 and 20 willbe described in further detail with reference to FIGS. 8A to 9C.

First, referring to FIG. 8A, the negative electrode electrolyte layer 12is disposed, e.g., attached, onto the negative electrode metal layer 11.The negative electrode metal layer 11 and the negative electrodeelectrolyte layer 12 may be separately formed and attached to each otheror the negative electrode electrolyte layer 12 may be directly formed onthe negative electrode metal layer 11.

The negative electrode metal layer 11 for occluding and emitting metalions may comprise lithium (Li), sodium (Na), zinc (Zn), potassium (K),calcium (Ca), magnesium (Mg), iron (Fe), aluminum (Al), an alloy of theforegoing, or combination thereof.

The negative electrode electrolyte layer 12 transports the metal ions tothe positive electrode layer 13. To do so, the negative electrodeelectrolyte layer 12 may include an electrolyte comprising a salt and asolvent, for example electrolyte formed by dissolving a metal salt in asolvent. In an embodiment, the electrolyte may be in a solid phase andmay comprise a polymer-based electrolyte, an inorganic-basedelectrolyte, or a composite electrolyte, such as an electrolyte obtainedby mixing the polymer-based electrolyte and the inorganic-basedelectrolyte. The electrolyte may be manufactured to be flexible tofacilitate subsequent processes. The metal salt may comprise, forexample, a lithium salt such as LiN(SO₂CF₂CF₃)₂, LiN(SO₂C₂F₅)₂, LiClO₄,LiBF₄, LiPF₆, LiSbF₆, LiAsF₆, LiCF₃SO₃, LiN(SO₂CF₃)₂, LiC(SO₂CF₃)₃,LiN(SO₃CF₃)₂, LiC₄F₉SO₃, LiAlCl₄, lithiumbis(trifluoromethanesulfonyl)imide (“LiTFSI”), or combination thereof.Also, another metal salt such as AlCl₃, MgCl₂, NaCl, KCl, NaBr, KBr,CaCl₂, or combination thereof may be added to the above-describedlithium salt. Any suitable material that may dissolve the lithium saltand the metal salt may be used as the solvent. Representative solventsinclude ethylene carbonate, butylene carbonate, dimethyl carbonate,methyl ethyl carbonate, diethyl carbonate, γ-butyrolactone, methylpropionic acid, butyl propionic acid, ethyl propionic acid, or acombination thereof.

In addition, the negative electrode electrolyte layer 12 may furtherinclude a separation layer (not shown) having suitable conductivity forthe metal ions while substantially or effectively preventingtransmission of oxygen. The separation layer may use a flexiblepolymer-based separation layer. For example, the separation layer maycomprise a polymeric non-woven fabric such as a non-woven fabriccomprising polypropylene or a non-woven fabric of polyphenylene sulfideand a porous layer, e.g., film, of olefin-based resin such aspolyethylene or polypropylene. The separation layer and the electrolytemay comprise separate layers. However, the negative electrodeelectrolyte layer 12 may comprise a single layer by impregnating poresof the porous separation layer with the electrolyte. For example, thepores of the porous separation layer may be impregnated with theelectrolyte, which may be formed by mixing polyethylene oxide (“PEO”)and LiTFSI so that the negative electrode electrolyte layer 12 may beformed.

Next, as illustrated in FIG. 8B, the positive electrode layer 13 isdisposed, e.g., coated, on the negative electrode electrolyte layer 12.The positive electrode layer 13 may include the electrolyte forconducting the metal ions, a catalyst for oxidation and reduction ofoxygen, a conductive material, and a binder. For example, after mixingthe above-described electrolyte, catalyst, conductive material, andbinder, a solvent may be added to manufacture a positive electrodeslurry, and the manufactured positive electrode slurry may be coated onthe negative electrode electrolyte layer 12 and dried so that thepositive electrode layer 13 may be formed.

Here, the electrolyte may include the above-described lithium saltand/or the metal salt. A porous carbon-based material, a conductivemetal material, a conductive organic material, or a combination of theabove may be used as the conductive material. For example, carbon black,graphite, graphene, activated carbon, carbon fabric, and carbonnanotubes may be used as the carbon-based material. The conductive metalmaterial may be used in the form of metal powder. Platinum (Pt), gold(Au), and silver (Ag) or an oxide of manganese (Mn), nickel (Ni), andcobalt (Co) may be used as the catalyst. In addition,polytetrafluoroethylene (“PTFE”), polypropylene, polyvinylidene fluoride(“PVDF”), polyethylene, styrene-butadiene rubber, or combinationthereof, may be used as the binder.

As illustrated in FIG. 8C, the first gas diffusion layer 14 a ispartially disposed on the positive electrode layer 13. Here, the firstgas diffusion layer 14 a absorbs oxygen in the air to supply theabsorbed oxygen to the positive electrode layer 13. To do so, the firstgas diffusion layer 14 a may have a porous structure so that externaloxygen may be smoothly diffused. For example, the first gas diffusionlayer 14 a may comprise a carbon paper such as a carbon fabric, carboncloth, or carbon felt, a metal foam such as a metal from having asponge-shape, or metal fabric mat.

After the first gas diffusion layer 14 a is disposed on the positiveelectrode layer 13, the negative electrode metal layer 11, the negativeelectrode electrolyte layer 12, and the positive electrode layer 13 arevertically bent so that the positive electrode layer 13 may contact oneside surface of the first gas diffusion layer 14 a without a gap. Forexample, remaining parts of the negative electrode metal layer 11, thenegative electrode electrolyte layer 12, and the positive electrodelayer 13 that are not covered with the first gas diffusion layer 14 amay be bent to be vertically erected.

Then, as illustrated in FIG. 8D, the erected negative electrode metallayer 11, negative electrode electrolyte layer 12, and positiveelectrode layer 13 are bent on the upper surface of the first gasdiffusion layer 14 a so that the positive electrode layer 13 may contactthe upper surface of the first gas diffusion layer 14 a without a gap.At positions that coincide with the ends of the negative electrode metallayer 11, the negative electrode electrolyte layer 12, and the positiveelectrode layer 13 under the first gas diffusion layer 14 a, thenegative electrode metal layer 11, the negative electrode electrolytelayer 12, and the positive electrode layer 13 on the first gas diffusionlayer 14 a may be vertically erected again.

Finally, referring to FIG. 8E, the vertically erected negative electrodemetal layer 11, negative electrode electrolyte layer 12, and positiveelectrode layer 13 are reversely bent by 180 degrees. Then, the negativeelectrode metal layer 11 is folded in a serpentine configuration to bestacked and the positive electrode layer 13 is exposed upward. Then, thesecond gas diffusion layer 14 b may be further disposed on the exposedpositive electrode layer 13. Then, as illustrated in FIGS. 8C and 8D,the negative electrode metal layer 11, the negative electrodeelectrolyte layer 12, and the positive electrode layer 13 may bedispose, e.g., bent, on the second gas diffusion layer 14 b.

In FIGS. 8A to 8E, it is illustrated that the metal-air battery 10includes two gas diffusion layers, namely, the first and second gasdiffusion layers 14 a and 14 b. However, the present embodiment is notlimited to the foregoing. The metal-air battery 10 may comprise only oneof the first and second gas diffusion layers 14 a and 14 b if desired ormay comprise three or more gas diffusion layers. After repeating theprocesses illustrated in FIGS. 8A to 8E in accordance with the number ofdesired gas diffusion layers 14 a and 14 b, the negative electrode metallayer 11, the negative electrode electrolyte layer 12, and the positiveelectrode layer 13 that are left after covering the upper surface of theuppermost gas diffusion layer are cut off so that the metal-air battery10 may be completed. For example, the negative electrode metal layer 11,the negative electrode electrolyte layer 12, and the positive electrodelayer 13 may be repeatedly bent so that the positive electrode layer 13contacts the lower and upper surfaces of the plurality of gas diffusionlayers, for example, the first and second gas diffusion layers 14 a and14 b. Here, between the two adjacent first and second gas diffusionlayers 14 a and 14 b, the negative electrode metal layer 11, thenegative electrode electrolyte layer 12, and the positive electrodelayer 13 are bent by 180 degrees so that the negative electrode metallayer 11 is folded in a serpentine configuration to be stacked and thepositive electrode layer 13 contacts the two first and second gasdiffusion layers 14 a and 14 b. Then, the same side surfaces of theplurality of gas diffusion layers, for example, the first and second gasdiffusion layers 14 a and 14 b, may be exposed to the outside.

In an embodiment, in order to manufacture the metal-air battery 20illustrated in FIG. 7, first, as illustrated in FIG. 8A, the negativeelectrode electrolyte layer 12 is disposed on, e.g., attached onto, thenegative electrode metal layer 11. Then, as illustrated in FIG. 9A, thefirst gas diffusion layer 14 a coated with the first and second positiveelectrode layers 13 a and 13 b is provided. For example, the positiveelectrode slurry manufactured by mixing the above-described electrolyte,catalyst, conductive material, and binder and then, adding the solventis coated on the lower and upper surfaces of the first gas diffusionlayer 14 a and dried so that the first and second positive electrodelayers 13 a and 13 b may be formed. Providing the negative electrodemetal layer 11, onto which the negative electrode electrolyte layer 12is disposed, and providing the first gas diffusion layer 14 a coatedwith the first and second positive electrode layers 13 a and 13 b neednot be sequentially performed.

As illustrated in FIG. 9B, the first gas diffusion layer 14 a ispartially dispose, e.g., arranged on, the negative electrode electrolytelayer 12. Then, the first positive electrode layer 13 a on the lowersurface of the first gas diffusion layer 14 a contacts the negativeelectrode electrolyte layer 12. Then, the negative electrode metal layer11 and the negative electrode electrolyte layer 12 are vertically bentso that the negative electrode electrolyte layer 12 may contact one sidesurface of the first gas diffusion layer 14 a without a gap. That is,the remaining portions of the negative electrode metal layer 11 and thenegative electrode electrolyte layer 12 that are not covered with thefirst gas diffusion layer 14 a may be bent to be vertically erected.

Referring to FIG. 9C, the vertically erected negative electrode metallayer 11 and negative electrode electrolyte layer 12 are bent on theupper surface of the first gas diffusion layer 14 a so that the negativeelectrode electrolyte layer 12 may contact the second positive electrodelayer 13 b on the upper surface of the first gas diffusion layer 14 awithout a gap. Then, in positions that coincide with the ends of thenegative electrode metal layer 11 and the negative electrode electrolytelayer 12 under the first gas diffusion layer 14 a, the negativeelectrode metal layer 11 and the negative electrode electrolyte layer 12on the first gas diffusion layer 14 a are vertically erected again andthen, the vertically erected negative electrode metal layer 11 andnegative electrode electrolyte layer 12 are reversely folded by 180degrees. Then, the negative electrode metal layer 11 is folded in aserpentine configuration to be stacked and the negative electrodeelectrolyte layer 12 is exposed upward.

Then, the second gas diffusion layer 14 b may be further disposed on theexposed negative electrode electrolyte layer 12. The lower and uppersurfaces of the second gas diffusion layer 14 b are contacted with,e.g., coated with, the first and second positive electrode layers 13 aand 13 b. Then, as described above, the negative electrode metal layer11 and the negative electrode electrolyte layer 12 may be bent on thesecond gas diffusion layer 14 b. After repeating the processesillustrated in FIGS. 9B and 9C in accordance with the number of requiredgas diffusion layers, namely, the first and second gas diffusion layers14 a and 14 b, the negative electrode metal layer 11 and the negativeelectrode electrolyte layer 12 that are left after covering the uppersurface of the uppermost gas diffusion layer are cut off so that themetal-air battery 20 may be completed. For example, the negativeelectrode metal layer 11 and the negative electrode electrolyte layer 12may be repeatedly bent so that the negative electrode electrolyte layer12 contacts the first and second positive electrode layers 13 a and 13 barranged on the lower and upper surfaces of the plurality of gasdiffusion layers, namely, the first and second gas diffusion layers 14 aand 14 b. Here, between the two adjacent first and second gas diffusionlayers 14 a and 14 b, the negative electrode metal layer 11 and thenegative electrode electrolyte layer 12 are bent by 180 degrees so thatthe negative electrode metal layer 11 is folded in a serpentineconfiguration to be stacked and the negative electrode electrolyte layer12 contacts the first and second positive electrode layers 13 a and 13b. Then, the same side surfaces of the plurality of gas diffusionlayers, namely, the first and second gas diffusion layers 14 a and 14 b,may be exposed to the outside.

As is further disclosed above, in the metal-air batteries 10 and 20according to the present embodiment, a ratio of the weight of thenegative electrode collector 15 to the total weight of the metal-airbatteries 10 and 20, excluding the outer casing 16, is small. Therefore,energy density (Wh/kg) of the metal-air batteries 10 and 20 according tothe present embodiment may be remarkably increased. For example, FIGS.11 and 12 are graphs illustrating energy density of the metal-airbattery 10 of FIG. 1 in comparison with a Comparative Example, and FIG.10 is a cross-sectional view schematically illustrating a structure of ametal-air battery 30 in the form of a two-dimensional cell according tothe Comparative Example used in the graphs of FIGS. 11 and 12. In thegraphs of FIGS. 11 and 12, a reaction area of the metal-air battery 10according to the Example and that of the metal-air battery 30 accordingto the Comparative Example are each 4 cm².

Referring to FIG. 10, the metal-air battery 30 in the form of atwo-dimensional cell according to the Comparative Example may include anegative electrode metal layer 31, a negative electrode electrolytelayer 32, a separation layer 33 having suitable conductivity for metalions while substantially or effectively preventing transmission ofoxygen, a positive electrode layer 34, a gas diffusion layer 36, and anouter casing 37 that surrounds remaining portions of the metal-airbattery 30 excluding the gas diffusion layer 36. In the metal-airbattery 30 in the form of a two-dimensional cell, when a plurality cellsare vertically stacked, oxygen may not be smoothly supplied to lowercells. In addition, since a ratio of a weight of a collector (not shown)for outputting current to the total weight of the metal-air battery 30is almost 50%, a ratio of the sum of the weights of the negativeelectrode metal layer 11, the negative electrode electrolyte layer 12,and the positive electrode layer 13 that contribute to the energydensity to the total weight of the metal-air battery 30 is small. Forexample, in the metal air battery 30 according to the ComparativeExample, the ratio of the sum of the weights of the negative electrodemetal layer 11, the negative electrode electrolyte layer 12, and thepositive electrode layer 13 to the total weight of the metal-air battery30 according to the comparative example may be less than about 35%. Onthe other hand, in the metal-air batteries 10 and 20 according to thepresent embodiment, since a ratio of the sum of the weights of thenegative electrode metal layer 11, the negative electrode electrolytelayer 12, and the positive electrode layer 13 to the total weight of themetal-air battery may be almost about 80%, for example about 30% toabout 80%, or about 40% to about 70%, energy density may be surprisinglyincreased.

For example, referring to the graph of FIG. 11, it is noted that, inboth the energy density in the case where the outer casing is includedand the energy density in the case where the outer casing is excluded,the energy density of the metal-air battery 10 according to the presentembodiment is about twice greater than that of the metal-air battery 30according to the Comparative Example. In addition, referring to thegraph of FIG. 12, it is noted that, in the metal-air battery 30according to the Comparative Example, the energy density is hardlychanged although the number of cells is increased, on the other hand, inthe metal-air battery 10 according to the present embodiment, the energydensity is increased as the number of cells is increased. For example,when the number of cells is one, the energy density of the metal-airbattery 10 according to the present embodiment is about twice greaterthan that of the metal-air battery 30 according to the ComparativeExample. However, when the number of cells is 20, the energy density ofthe metal-air battery 10 according to the present embodiment is aboutthree or more times greater than that of the metal-air battery 30according to the Comparative Example.

It should be understood that the exemplary embodiments described hereinshould be considered in a descriptive sense only and not for purposes oflimitation. Descriptions of features, advantages, or aspects within eachembodiment should typically be considered as available for other similarfeatures, advantages, or aspects in other embodiments.

While one or more embodiments of the present disclosure have beendescribed with reference to the figures, it will be understood by thoseof ordinary skill in the art that various changes in form and detailsmay be made therein without departing from the spirit and scope of thepresent disclosure as defined by the following claims.

What is claimed is:
 1. A metal-air battery comprising: a negativeelectrode metal layer disposed on a first side of a negative electrodeelectrolyte layer; a first positive electrode layer disposed on anopposite second side of a first portion of the negative electrodeelectrolyte layer, the first positive electrode layer comprising apositive electrode material which is capable of using oxygen as anactive material; a gas diffusion layer disposed on a side of the firstpositive electrode layer which is opposite the negative electrodeelectrolyte layer; and a second positive electrode layer disposed on aside of the gas diffusion layer which is opposite the first positiveelectrode layer, wherein a first portion of the negative electrodeelectrolyte layer is between the first positive electrode layer and afirst portion of the negative electrode metal layer, wherein a secondportion of the negative electrode electrolyte layer is between thesecond positive electrode layer and a second portion of the negativeelectrode electrolyte layer, wherein the negative electrode metal layerand the negative electrode electrolyte layer are disposed on the firstand second positive electrode layers so that the negative electrodeelectrolyte layer contacts an upper surface of the first positiveelectrode layer and a lower surface of the second positive electrodelayer, wherein an upper surface of the gas diffusion layer contacts thelower surface of the first positive electrode layer, wherein a lowersurface of the gas diffusion layer contacts the upper surface of thesecond positive electrode layer, wherein a first side surface of the gasdiffusion layer is exposed to the outside, and wherein a second sidesurface of the gas diffusion layer, which is opposite the first sidesurface of the gas diffusion layer, connects the upper surface of thegas diffusion layer and the lower surface of the gas diffusion layer,wherein the negative electrode metal layer and the negative electrodeelectrolyte layer are bent so that the negative electrode metal layerand the negative electrode electrolyte layer, are in a foldedconfiguration and surround the upper surface, the lower surface, and thesecond side surface of the gas diffusion layer.
 2. The metal-air batteryof claim 1, wherein the gas diffusion layer comprises a plurality of gasdiffusion layers, wherein first and second positive electrode layers aredisposed on upper and lower surfaces of each gas diffusion layer of theplurality of gas diffusion layers, respectively, and wherein thenegative electrode metal layer and the negative electrode electrolytelayer are repeatedly bent so that the negative electrode electrolytelayer contacts the first positive electrode layer and the secondpositive electrode layer.
 3. The metal-air battery of claim 2, wherein,between adjacent gas diffusion layers, the negative electrode metallayer and the negative electrode electrolyte layer are bent by 180degrees so that the negative electrode metal layer is foldedconfiguration and the negative electrode electrolyte layer contacts thefirst positive electrode layer and the second positive electrode layer.4. The metal-air battery of claim 2, wherein same first side surfaces ofeach gas diffusion layer of the plurality of gas diffusion layers areexposed to the outside.
 5. The metal-air battery of claim 1, furthercomprising a negative electrode collector which contacts a bend portionof the negative electrode metal layer and extends in a directionperpendicular to a major surface of each of the negative electrode metallayer, the negative electrode electrolyte layer, the positive electrodelayer, and the gas diffusion layer.
 6. The metal-air battery of claim 1,wherein an end of an exposed first side surface of the gas diffusionlayer protrudes from the negative electrode metal layer, the negativeelectrode electrolyte layer, and the first and second positive electrodelayers.
 7. The metal-air battery of claim 1, wherein the negativeelectrode electrolyte layer comprises a separation layer which isionically conductive and substantially impermeable to oxygen, and anelectrolyte.